Stricter regulation of pollutants in the exhause gas of internal combustion engines, in particular automobile engines, together with the desirability of increased efficiency in fuel consumption, render precise fuel apportioning, as well as delivery under optimum conditions, imperative. In conventional carburetor installations, precise apportionment of small fuel quantities uniformly among the individual cylinders is difficult because large portions of the fuel condense on the walls of the intake passage and run along in the form of droplets. This not only makes fuel apportionment considerably more difficult, but also results in poorer performance of the engine, particularly at unsteady operating states. This condition may be improved by providing a fuel injection device for injecting fuel in precise quantities into the intake ports of the individual cylinders.
In internal combustion engines operating with a supercharging compressor in the intake passage, for example, an exhaust driven supercharging compressor, similar conditions prevail. Additional difficulties result, however, since the compression of the intake air will cause a temperature rise, with the danger of knocking, especially at higher loads. Knocking becomes especially noticeable if a fuel injection device as described above is employed. Knocking will be less acute in carburetor installations where the fuel is added to the air before passing through the compressor, since as the fuel in the mixture vaporizes, it will absorb heat thus tending to reduce the temperature of the compressed mixture.